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Revista Brasileira de Geofısica (2014) 32(3): 539-548© 2014 Sociedade Brasileira de GeofısicaISSN 0102-261Xwww.scielo.br/rbg

PHOSPHORITES OF THE BRAZILIAN CONTINENTAL MARGIN,SOUTHWESTERN ATLANTIC OCEAN

Jose Gustavo Natorf de Abreu1, Iran Carlos Stalliviere Correa2,Norberto Olmiro Horn Filho3 and Lauro Julio Calliari4

ABSTRACT. The existence of phosphate deposits in the Brazilian continental margin is known since the 1970’s and 1980’s after the Global Recognition of the Brazilian

Continental Margin Program – REMAC Project (Programa de Reconhecimento Global da Margem Continental Brasileira – Projeto REMAC) a joint program to explore

the Brazilian continental margin. Phosphate deposits were collected on the seamounts offshore the northeastern Brazilian margin. In the early 2000’s, phosphate sampleswere taken incidentally by demersal fishing fleet in the southern Brazilian continental margin which contributed to the knowledge of these deposits in the southwestern

Atlantic. This paper describes the mineralogy of the samples with scanning electron microscopy and X-ray diffraction. The new phosphate deposits in the Braziliancontinental margin suggests a much wider phosphate distribution than imagined in the REMAC publications, thus representing a contribution to the effort of the Brazilian

Government, through the Ministry of Mines and Energy, the Geological Survey of Brazil (CPRM), the Inter-ministerial Commission for the Resources of the Sea and

the Marine Geology and Geophysics Program who together undertake a Program to the Evaluation of the Mineral Potential of the Brazilian Legal Continental Shelf(REMPLAC), whose goal is to conduct a further investigation of the mineral potential of the Brazilian Territorial Sea and Exclusive Economic Zone (EEZ).

Keywords: marine mineral resource, phosphate deposits, Rio Grande Terrace.

RESUMO. A existencia de depositos fosfaticos na margem continental brasileira e conhecida desde as decadas de 1970 e 1980, gracas ao Projeto de Reconhecimento

Global da Margem Continental Brasileira (REMAC) quando fosforitas foram recolhidas sobre os montes submarinos da regiao Nordeste. No inıcio dos anos 2000,amostras foram obtidas incidentalmente pela frota pesqueira demersal na margem continental sul brasileira, as quais foram incorporadas como novas ocorrencias,

contribuindo para o conhecimento destes depositos no Atlantico sul ocidental. Este trabalho descreve a mineralogia deste material amostrado a partir de analisesrealizadas com microscopio eletronico de varredura e difratometria de raios X. A localizacao das novas ocorrencias de depositos fosfaticos na margem continental

brasileira sugere uma distribuicao bem mais ampla desses recursos minerais marinhos do que se imaginava ate as publicacoes do REMAC, representando, portanto,uma contribuicao ao esforco do governo brasileiro, atraves do Ministerio de Minas e Energia, do Servico Geologico do Brasil, da Comissao Interministerial para os

Recursos do Mar e do Programa de Geologia e Geofısica Marinha que, juntos, empreendem o Programa de Avaliacao da Potencialidade Mineral da Plataforma Continental

Jurıdica Brasileira (REMPLAC), cuja meta e realizar estudos mais aprofundados sobre a potencialidade mineral do Mar Territorial Brasileiro e da Zona Economica Exclusiva(ZEE).

Palavras-chave: recurso mineral marinho, depositos fosfaticos, Terraco do Rio Grande.

1Universidade do Vale do Itajaı (LOG/CTTMar/UNIVALI), Geological Oceanography Laboratory, Center for Technology of Earth and Marine Sciences, Rua Uruguai,

458, Setor E2, P.O. Box 360, Centro, 88302-202 Itajaı, SC, Brazil. Phone: +55(47) 3341-7718 – E-mail: [email protected] Federal do Rio Grande do Sul (CECO/IG/UFRGS), Department of Geodesy, Institute of Geosciences, Rua Bento Goncalves 9500, Building 43125,

P.O. Box 15.001, Bairro Agronomia, 91501-970 Porto Alegre, RS, Brazil. Phone: +55(51) 3308-9855 – E-mail: [email protected] Federal de Santa Catarina (GCN/CFH/UFSC), Department of Geosciences, Graduate Program in Geography, Center for Philosophy and Humanities,

Campus Universitario Trindade, 88040-970 Florianopolis, SC, Brazil. Phone: +55(48) 3721-9664 – E-mail: [email protected] Universidade Federal do Rio Grande (IG/LOG/FURG), Oceanographic Institute, Laboratory of Geological Oceanography, Av. Italia Km 8, P.O. Box 474,

Campus Carreiros, 96201-900 Rio Grande, RS, Brazil. Phone: +55(53) 3233-6518 – E-mail: [email protected]

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540 PHOSPHORITES OF THE BRAZILIAN SOUTH CONTINENTAL MARGIN

INTRODUCTION

Phosphate in the marine environment

Phosphorus is an essential element for the life processes of plantsand animals, occurring with relative abundance on Earth as phos-phate in three different depositional types: (1) guano – organicdeposit with low economic importance; (2) aluminum phosphate– mineral with some economic importance; and (3) calcium phos-phate – the most important natural phosphate mineral depositwith high economic importance.

Phosphate may be found either in the continent or in the ma-rine environment. On the continent may be associated with ig-neous, sedimentary and metamorphic rocks, as an accessory inmost cases. Local enrichment of phosphate minerals may occurdepending on factors such as mineralogy of the primary rocks, hy-drothermalism and weathering (Born & Kahn, 1990). The marineenvironment is primarily a sedimentary deposit whose formationis related to the phosphorus inflow to the oceans (Baturin, 1982;Ruttenberg & Berner, 1993 apud Schenau et al., 2000). Marinephosphorites were sampled for the first time during the dredg-ing done by the Challenger Expedition (1873-1876) on the Agul-has Bank, in South Africa (Murray & Renard, 1981 apud Bentor,1980). Since then similar occurrences were recorded in severalother places on the ocean bottom.

In addition to phosphorus inflow, the formation of phospho-rite is also related to nitrogen inflow, both being supplied by up-welling currents and mechanisms involving organic matter andbiogeochemical processes (Sheldon & Riggs, 1990). In seawater,phosphate (PO−34 ) is suspended or dissolved in organic and inor-ganic forms. It is transported to the marine environment throughriver and underground inflow, volcanic and hydrothermal activ-ity, rainfall, glacial discharges, coastal abrasions and even bythe cosmic dust present on the Earth surface. Phosphate canalso occur as guano and excretion of other marine organisms(Baturin, 1982).

The phosphate cycle in the ocean starts with the supply tothe oceans, continues with the initial assimilation by phytoplank-ton organisms and transfers to the food chain of fish and marinemammals (Baturin, 1982). Finally, with the excretion and poste-rior deposition on the sediments, the phosphate becomes avail-able to form phosphorite. Once recycled, through the metabolismof organisms and the action of bacteria and/or enzymes that de-compose organic matter, phosphorus is returned to the environ-ment and “re-mineralized” along with other nutrients, in upwellingzones (Brown et al., 1995).

Currently, the largest and most important upwelling zones inthe world are located on the eastern edges of ocean basins where

significant phosphate deposits occur. Burnett & Riggs (1989)described important phosphogenesis events on the west coastof the United States associated with upwelling currents andbathymetry, favorable conditions accounted for in the model, forthe time of upper Oligocene and the Quaternary.

These natural processes, responsible for the supply and con-centration of phosphorus in the marine environment, result in anenrichment of up to 80% of this element in marine phosphaterocks, predominantly sedimentary, which are then called phos-phorites. Under the assessment of the Program to the Evaluationof the Mineral Potential of the Brazilian Legal Continental Shelf(REMPLAC), the geological mapping of phosphorite depositswas included among the activities that should reveal the mineralpotential of the continental margin. The evaluation of potentialphosphorus reserves on the Brazilian continental margin repre-sents the incorporation of the data to the national reserves statis-tics, as well as production and marketing of phosphates, whichare raw materials for a range of products used to manufacturefertilizers and in the chemical industry.

In addition to the research about the potential phosphate de-posits on the Brazilian continental margin, this study will con-tribute to other branches of marine science that address paleo-ceanography, climate change and related sea level changes sincephosphorite formation is related to upwelling processes; mecha-nisms that have been occurring along the geological time.

Phosphorite: concept, origin and age

Phosphorite is an authigenic sedimentary rock that contains vary-ing amounts of phosphate (Notholt, 1980; Slansky, 1986), pre-dominantly in the form of apatite and hydroxyapatite. Amongthese, francolite is considered the most common phosphatemineral originated by recent diagenesis in marine environments(McClellan, 1980). It may also constitute a fibrous variety of ap-atite, such as tricalcium phosphate of sedimentary origin. It dis-plays a cryptocrystalline or amorphous structure, of sandy orclayey texture, usually associated with calcium and magnesiumcarbonates, iron and aluminum oxides and uranium traces. Phos-phorites may occur as pebbles, nodules or crusts.

Phosphorite occurs at the edges of continental shelves andupper continental slopes, in middle and low latitude regions, withreduced terrigenous sedimentation (Burnett, 1977) and maximumdepth of 1,000 m (Silva & Mello, 2004). It may also occur onthe top of ridges and submarine plateaus that work as barriers tothe flow of cold bottom currents, rich in nutrients like phospho-rus. In these places, upwelling currents are at lower depths pre-vailing heated and oxidized waters, decreasing the solubility of

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ABREU JGN, CORREA ICS, HORN FILHO NO & CALLIARI LJ 541

phosphorus by a lower pH. Hence, phosphorus precipitates andenriches the sediment (Kasakov, 1937 apud Menor et al., 1979).

Previous works have highlighted four large and importantphosphorite provinces in the oceans:

– East Atlantic (Tooms & Summerhayes, 1968; Dingle,1970, 1971; Summerhayes, 1970, 1972; Baturin et al.,1973; Emery et al., 1975; Kharin & Soldatov, 1975);

– West Atlantic (Pratt & Thompson, 1962; Gorsline & Milli-gan, 1963; Pratt & Manhein, 1968; Pratt, 1968; Sheridanet al., 1969; Hathaway, 1971);

– Pacific, on the California coast (Emery & Dietz, 1950;Uchupi & Emery, 1963; D’Anglejan, 1967) and on theChilean-Peruvian coast (Murray & Renard, 1891; Niino& Chamberlain, 1961; Baturin & Petelin, 1972; Burnett,1974, 1977; Baturin et al., 1973).

The largest ever recorded phosphorite occurrences in thecontinental shelf of Morocco, although the results have beenpublished only in brief communications (Baturin, 1969, 1971;Bremner, 1980).

The theories on the formation of phosphorite consider di-rect match precipitation through chemical interactions in saturatedphosphate solutions and the metasomatic replacement of pre-existing carbonate deposits, becoming apatite. This hypothesisis the most probable to explain phosphorite formation, however,whatever the reactions involved, the formation of the deposits isstrongly dependent on the availability of phosphorus in the marineecosystem. Besides the phosphate material, non-phosphate com-ponents are present in the mineralogical composition of marinephosphorite, which also proves its autochthonous origin. Glau-conite and shells of foraminifera are observed in some concre-tions; however, the presence of non-phosphate components de-pends on environmental characteristics and adjacent sediments.

The process of phosphorite origin can be influenced by spe-cific physic-chemical conditions prevailing during periods oftransgression and regression. Transgressive periods are morefavorable due to increased precipitation of solids and solublecompounds derived from higher productivity, the presence ofmore stagnant and phosphorus saturated basins and water back-ground with minimum levels of O2 (Fischer & Arthur, 1977;Sheldon, 1980), characteristic of these periods.

Phosphatization begins with the accumulation of precipita-tion in small nucleus that also corresponds to the beginning ofapatite formation (Baturin, 1971). Kolodny (1980), Baturin (1971and 1988), Glenn & Arthur (1988), and Burnett & Riggs (1989)described that phosphatization may have biogenic remains, such

as foraminifera, fish bones and teeths with consequent formationof microcrystalline fluorapatite. The presence of debris from clamshells, corals, sea urchins and various other marine organismgroups, partially or completely replaced, are examples of mate-rials which can pass through the replacement process (Burnett &Riggs, 1989). A second phase is the enrichment and mechanicalconcentration through the reworking of primary deposits duringa later regression. The higher energy and more oxidizing envi-ronment, prevails accumulation of rich nodules with glauconite,dolomite and other iron oxides (Baturin, 1971; Kolodny, 1980;Baturin, 1988; Glenn & Arthur, 1988; Burnett & Riggs, 1989). Inshallower waters, the fine carbonate sediments are the ideal nu-cleus for the apatite crystallization (Stum & Leckie, 1977 apudBurnett & Riggs, 1989).

Dating performed from the 67Sr/66Sr ratio suggest differentages for the start of the phosphogenesis ranging between 29.8and 3.4 Ma BP (Jarvis et al., 1994). This variability depends onthe formation site and the variation of the local concentrationsof phosphorus, calcium and fluorine that make up the phospho-rites. In Namibia, the age of phosphorite pellets was determinedas middle Miocene and even Pleistocene (0.4 Ma BP) while, inthe desert of Sechura, Peru, the ages were about 8.9 Ma BP.The process of phosphatization in Cape Province in South Africahas been occurring recently, during the Pleistocene and theHolocene, although the carbonate matrix has formed, according toJarvis et al. (1994), between the Miocene and the Pliocene (18.5and 3.4 Ma BP).

The phosphorite studied in Brazil by Klein et al. (1992,1993) were aged 32.8 ± 6.4 Ma BP placing the samples inthe Oligocene. In addition to the radiocarbon dating of thesamples collected recently, other chemical and mineralogicalanalyses must be performed to correlate the occurrences on theBrazilian continental margin to other regions of the world wherephosphorite is formed.

Phosphorite occurrences in Brazil

In Brazil, the occurrence record of marine phosphorite is small.The environmental conditions for phosphorite formation shouldbe better characterized and further detailed in order to evaluatemore carefully this mineral resource on the Brazilian continentalmargin.

The largest phosphorite occurrences in the oceans are re-lated to areas influenced by strong upwelling, which is morepronounced on the western margins of the continents (Baturin,1971). However, Riggs & Sheldon (1990) model suggested thatthe Brazilian coast could present favorable conditions for phos-

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phogenesis. So far, occurrences of phosphate deposits are citedby Millimann & Amaral (1974); Melo et al. (1978), Guazelli &Costa (1978), Menor et al. (1979), Schobbenhaus (1984) andSantana (1999), in works carried out on the terraces and sub-marine plateaus in northeastern Brazil. Klein et al. (1992) werethe first to describe evidences of phosphorite deposits in samplesfrom the Rio Grande Terrace (RS), in southern Brazil.

Samples collected accidentally by the fishing fleet, between200 and 800 m deep, offshore the states of Rio Grande do Sul,Santa Catarina and Parana during the Program of the SustainablePotential of Living Resources of the Exclusive Economic Zone –REVIZEE (1997 to 2000), suggest a possible wider distributionof the phosphate deposits on the southern Brazilian continentalmargin, added to the occurrences on the Brazilian northeasterncontinental margin.

The samples described in this study were obtained in thecontinental margin close to the Florianopolis Shelf and RioGrande Terrace, located between the southern Santa Catarina andnorthern Rio Grande do Sul. Florianopolis Shelf presents sub-provinces of the outer continental shelf and upper continentalslope that appear as protruding features of the continental mar-gin as demonstrated by the broad curvature of the isobaths. Fig-ure 1 shows the location and distribution of phosphorite samplescollected in the region, based on the study of Abreu et al. (2005).

The relief is extremely irregular in some specific sectors ofthis continental margin, as indicated by an echosounder recordobtained in 1997 on board the survey vessel Diadorim, duringREVIZEE Program (REVIZEE, 1997), whose sonogram showssharp peaks of 12 m high (Fig. 2).

Data collected during REVIZEE Program were published byPinho et al. (2011) suggesting the presence of phosphorite incertain areas of the continental shelf and continental slope ofthe southern Brazilian region. The study took into account thebackscattering observed in the 38 kHz echosounder records thatindicate high hardness and compaction of the seafloor. The ir-regular morphology and the high backscattering of the seafloorindicate the compact nature of the seabed that may be related tothe presence of phosphorite crusts, as evidenced by the samplescollected in this area. Table 1 shows the location of the samplingstations and the results of petrographic analyses performed withthis material.

Mineralogical analysis

The mineralogical composition of the collected samples was de-termined by X-ray diffraction and thin sections were analyzed byscanning electron microscope (SEM).

The main components were apatite, calcite and dolomite, de-rived from the replacement of calcium by the magnesium presentin the seawater, through a diagenetic process, and quartz, whichis the only mineral present in all samples. Among the phosphateminerals, carbonate fluorapatite and hydroxyapatite predominatedin the samples, which were probably formed by carbonate re-placed by phosphate and due to the high ionic affinity betweenfluorine and phosphorus. Other minerals identified by X-ray weregoethite, witherite, phillipsite, baryte and carbonate fluorapatite,which are associated with the processes of replacement and/oradsorption of the elements on the phosphate rocks. Figure 3shows the diffractograms of AM-01, AM-04, AM-06 and AM-13 samples, indicating the main minerals contained in them. TheAM-12 mineralogical analysis performed by SEM (Fig. 4A) in-dicated the presence of quartz, apatite, glauconite, and dolomitewrapped in a phosphate matrix (Fig. 4B).

The mineralogical analysis of sample AM-13 (Fig. 5) indi-cated the presence of sediment well sorted, grains of quartz andapatite and traces of foraminifera and ostracods microfossils,confirming the authigenic origin of the phosphorite. The carbon-ate matrix is replaced by the phosphate matrix to the extent of thephosphatization process. Figure 5 shows the contact between thephosphate and carbonate matrix, besides of quartz, glauconite,apatite, dolomite and goethite. The phosphatization process thatinvolves the replacement of biogenic calcium carbonate (CaCO3)by phosphate (PO−34 ) was discussed in Romankevich & Baturin(1972) and Baturin (1982). According to Slansky (1986), thisprocess is relatively common in the genesis of phosphorite.

DISCUSSION AND CONCLUSION

The phosphorite samples collected on the surface of the Flo-rianopolis Shelf and Rio Grande Terrace indicates that thismineral occurs in the Northeast region of Brazil as well as thesouthern continental margin. Acoustic backscattering recordsobtained and analyzed during the REVIZEE Program indicated theexistence of a submarine floor quite compacted and hardenedcorroborating the possibility of a more significant occurrence ofphosphorite at the outer edge of the Florianopolis Shelf and RioGrande Terrace, prominent features of the southwestern Atlanticocean.

Menor et al. (1979) described the occurrence of phosphoriteon the Ceara and Rio Grande do Norte plateaus in northeasternBrazil. The authors correlated the phosphorite formation to thecirculation of cold deep waters, rich in phosphorus and othernutrients that upon meeting the submarines highs and plateausthese waters are pushed upwards causing upwelling. The phos-


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Figure 1 – Location of the sites where phosphorite samples were collected during various research projects developed in the South region of Brazil, modified fromAbreu et al. (2005). Datum WGS 1984.

Figure 2 – Echogram obtained on board the survey vessel Diadorim during REVIZEE Program (REVIZEE, 1997).

phate present in the water precipitates inorganically due to de-creased solubility of lower pH and oxidizing environment, uponreaching shallower and warmer areas (Kasakov, 1937 apud Menoret al., 1979). The Florianopolis Shelf and Rio Grande Terraceare located on the southern continental margin of Brazil stronglyinfluenced by different water masses causing gradients of tem-perature, salinity and dissolved O2 concentration, among otheroceanographic parameters. The South Atlantic Central Water –

SACW (Sverdrup et al., 1942), that moves towards south south-west following the continental shelf break and continental slope,between 200 and 500 m deep, is rich in nutrients and oxygen,and may have seasonal flows toward the continental shelf (Cas-tro Filho & Miranda, 1998) favoring the upwelling occurrence(Pereira et al., 2009). The region is also influenced by the Mal-vinas current that moves towards north northeast and is respon-sible for the supply of inorganic nutrients to shallower regions,


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Table 1 – Geographical position and main components of the analyzed samples.

Sample Lat. (S) Long. (W) Depht (m)P2O5 Main components

(%) concentrationQuartz, Dolomite, Goethite,

AM-01 31◦02.138’ 49◦22.346’ 310 — Carbonate Fluorapatite,Hydroxyapatite

Dolomite, Quartz, Goethite,AM-04 27◦44.140’ 47◦06.787’ 530 5.39 Carbonate Fluorapatite,

HydroxyapatiteQuartz, Dolomite,

AM-06 29◦44.825’ 47◦49.989’ 495 1.19 Goethite, Phillipsite,Baryte

Quartz, Phillipsite, Baryte,AM-12 29◦18.864’ 47◦52.500’ 420-490 3.94 Carbonate Fluorapatite,

ChlorapatiteDolomite, Quartz,

AM-13 29◦37.708’ 48◦00.499’ 350-380 2.34 Phillipsite, Goethite,Carbonate Fluorapatite

Figure 3 – X-ray diffractogram of AM-01, AM-04, AM-06, and AM-13 samples indicating the main minerals present.

close to the mainland. The bathymetry of the Florianopolis Shelfand Rio Grande Terrace, associated with the wind regime and sea-sonal flows, favors the formation of upwelling phenomenon thatis responsible for the increase in primary biological productivity,due to the supply of nutrients and consequently, the accumulationof limestone bioclasts, fish bones and other marine organisms.

Microfossils of foraminifera and ostracods observed in one of theblades attest the association between phosphorite formation andbioclasts. The limestone matrix identified confirms the relation-ship of carbonate, which may originate from the dissolution ofcalcareous bioclasts, under phosphatization processes. The au-thigenesis was also suggested by occurrence of glauconite in the


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Figure 4 – Macroscopic sample AM-12 (A) and its thin section (B). Note the presence of carbonate dolomite in the phosphatematrix and other accessory minerals such as quartz and glauconite.

Figure 5 – (A) Macroscopic aspect of the AM-13 sample obtained in the vicinity of Santa Marta Grande cape (SC); and (B),Thin section showing the contact between the phosphate and carbonate matrix with foraminifera carapace, being identifiedquartz and apatite, traces of microfossils (foraminifera and ostracods).

phosphate deposit. In addition to this mineral, quartz, dolomiteand goethite were also identified, indicating a diagenetic originfor phosphorite whether conglomerate or nodular.

The age of the analyzed phosphorite samples was not deter-mined and, therefore, cannot be compared with the samples de-scribed by Klein et al. (1992) and Klein et al. (1993) collected fromthe continental slope of Rio Grande do Sul, with respect to thetime and environmental conditions of formation. However, thelower levels of P2O5 determined for the samples collected fromthe Rio Grande Terrace and Florianopolis Shelf compared to thesamples collected farther south may be related to the lower rateof phosphorus inputs from the continent in this area compared tothe other region. The Rio Grande do Sul continental drainage net-work, before being isolated by the closure of the lagoon-barrier

depositional system of Pleistocene and Holocene (Villwock &Tomazelli, 1995; Tomazelli & Villwock, 1996; Tomazelli et al.,2000) was reaching the ocean basin more significantly, whencompared with the lower expression of Santa Catarina drainage.This may be responsible for a minor contribution condition anda reduced availability of phosphorus to the area where phospho-rite is formed. Anyway, new geochronological and mineralogicalanalyses should be performed to correlate the phosphorite presenton the surface of the Rio Grande Terrace and Florianopolis Shelfwith that occurring in the Rio Grande do Sul continental slope andin other areas of the Brazilian continental margin.

Geological and geophysical surveys should be carried out inmore detail in the short and medium term, to supply basic infor-mation to future projects.


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ACKNOWLEDGEMENTSThe authors are thankful to the Center for Research and Man-agement of Fishery Resources on the Southeast and South Coast– CEPSUL/ICMBio for supplying the echo bathymetric data ob-tained in 1997 by the Diadorim research vessel.

To Dr. Vitor Paulo Pereira of the Department of Mineral-ogy and Petrology of the Geosciences Institute (UFRGS), RicardoPiazza Meireles and Jose Eloi Guimaraes Campos from the X-rayDiffraction Laboratory (UnB) for the preparation and descriptionof the thin sections used in this study.

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Recebido em 2 outubro, 2012 / Aceito em 11 dezembro, 2013

Received on October 2, 2012 / Accepted on December 11, 2013

NOTES ABOUT THE AUTHORS

Jose Gustavo Natorf de Abreu graduated in Oceanography (FURG/1984), holds a Master in Marine Geology (LAGEMAR-UFF/1998) and PhD in Geosciences(UFRGS/2010). Currently, is a Professor of the undergraduate Oceanography at the Universidade do Vale do Itajaı (UNIVALI). Develops research in geomorphology,sedimentology, marine geophysics and exploration of mineral resources of the sea.

Iran Carlos Stalliviere Correa graduated in Geology (UFRGS/1973), holds a Master in Geosciences (UFRGS/1979) and Doctor of Oceanology (University of Bor-deaux I-France/1990). Currently, is a Professor of the Department of Geodesy and the Graduate Program in Geosciences at the Universidade Federal do Rio Grandedo Sul (UFRGS). CNPq researcher 1D.

Norberto Olmiro Horn Filho graduated in Geology (UNISINOS/1979), holds a Master and PhD in Geosciences (UFRGS/1988 and 1997). Currently, is a Professorof the Department of Geosciences and Geography Graduate Program at the Universidade Federal de Santa Catarina (UFSC). CNPq researcher 2.

Lauro Julio Calliari graduated in Oceanography (FURG/1975), holds a Master in Geosciences (UFRGS/1980) and PhD in Marine Science (College of William andMary-Virginia Institute of Marine Science/1990). Currently, is a Professor at the Institute of Oceanography at the Universidade Federal do Rio Grande (FURG). CNPqresearcher 1C.


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